In the Opening, you must develop pieces quickly. If you waste time capturing pawns, the position will become worse.
Example 1 1. d2-d4 d7-d5 2. Bc1-f4 Ng8-f6 3. Ng1-f3 e7-e6 4. e2-e3 c7-c5 5. c2-c4 in QP openings, the c-pawn is used by both players to attack the enemy pawn center 5. ..... Nb8-c6 6. Nb1-c3 a7-a6 7. Qd1-a4? better Ra1-c1 Bc8-d7 8. Qa4-d1 Qd8-a5 threat Nf6-e4 9. Qd1-b3? better Qd1-d2 d5xc4 10. Qb3xb7?? grabbing this poisoned pawn leads to immediate loss 10. ----- Ra8-a7! 11. White Resigns white Q is trapped since white moved his Q too many times in the opening
Example 2 1. e2-e4 c7-c5 2. Ng1-f3 d7-d6 3. d2-d4 c5xd4 4. Nf3xd4 g7-g6 5. c2-c4 Ng8-f6 6. Nb1-c3 Nb8-c6 7. f2-f3 Qd8-b6? correct is Bf8-g7 8. Bc1-e3! Qb6xb2?? grabbing this poisoned pawn leads to immediate loss. Better move was Qb6-d8 9. Nc3-a4 Qb2-a3 10. Be3-c1! Qa3-b4+ 11. Bc1-d2 Qb4-a3 12. Nd4-b5 Black Resigns black Q is trapped since black moved his Q too many times in the opening
When the 2 kings are separated by odd number of squares (1,3,5), they are said to be in opposition. Whoever has to play in opposition, their position becomes worse.
W: Ke4, c4 B: Ke7 White to Play and Win
1. Ke5! giving the opposition to black Kd7 2. Kd5 Kc7 3. Kc5! Kd7 4. Kb6 Kc8 5. Kc6! to win, your King must come to the 6th Rank and be in front of the passed pawn 5. .... Kd8 6. c5 Kc8 7. Kd6 Kd8 8. c6 giving the opposition to black Kc8 9. c7 Kb7 10. Kd7 Kb6 11. c8(Q) +-
More about Opposition: Wiki, ChessInsights Play through a very instructive example on ChessDotCom